Thermal responsive device



Feb. 7, 1928.

A. COHN ET AL THERMAL RESPONSIVE .DEV'ICE Filed March 5, 1927 Inventors AlFPed Cohn,

Kurt Muller,

www-

Thei r Attorney.

Patented Feb. 7, 19 28. I

UNITED STATES v v V 1,666,669 PATENT OFFICE.

ALFRED COHN, or CHARLOTTENBURG, AND KURT MULLER, or FRIEDENAU, GER- MANY, ASSIGNORS T0 GENERAL ELECTRIC COMPANY, A CORPORATION on NEW YORK.

THERMAL REsroNswE DEVICE.

Application filed March 3, 1927, Serial No. 172,537, and in Germany June 2, 1926.

This invention relates to thermal responsive devices, particularly current conducting bimetallic actuating mechanisms for overload relays, circuit interrupter trips, mlgasuring or indicating instruments or the li e. 6

The principal object of the invention is to provide an actuating mechanism of the above character having an improved construction of the bimetallic strips that permits a more secure mounting thereof as well as facilitates the connection thereof in an electric circuit and in addition enablgs a powerful rotary movement to be obtained directly from the bimetallic strips.

Bimetallic strips of the ordinary construction which are traversed by current and which serve for producing movements for thermal overload current relays, releases, measuring or indicator instruments, have the. disadvantage that the strips can only be firmly secured at one end'while the other end which bends out under the influence of the heating must be provided with a flexible thereof.

currentconnection. Such flexible connections, particularly for high current strengths form an element of construction both inconvenient and unreliable. Now, it is known that this flexible connection can be avoided by slitting a bimetallic strip U-shaped and by conducting the current through the U arms connected in series and provided with fixed connecting pieces. This entails, however, on theonehand, waste of material because the sawed out piece of the expensive bimetallic material cannot .be further utilized, and on the other hand, it is not applicable where the construction requires that the longitudinal axis of, the bimetallic formation bein alignment with the conductor with the connecting terminals at the opposite ends The present invention provides a'practical arrangement for overcoming the difficulties noted above. The arrangement of the present invention has the further advantage that it also supplies rotary movements without any auxiliary means. Moreover the power of the movement produced with the same overall length of construction under conditions which are otherwise equal, is con siderably greater with the improved construction of-the present invention than in the case of a single or U-shaped slit strip.

Inthe accompanying drawing, Fig. l is a plan view of a thermal responsive actuating mechanism showing schematically the arrangement of the current conducting bimetallic strips in accordance with a preferred form of the invention; Fig. 2 is a perspective view illustrating more in detail the construction of the thermal responsive actuating mechanism of Fig. 1; Fig. 3 shows schematically a modified form of actuating mechanism which is illustrated more in detail n Fig. 4; and Fig. 5 shows a further modification involving a plurality of bime talhc strips in cooperating relation.

The preferred arrangement in accordance w th the invention consists, as indicated in Fig. l, of two bimetallic strips Z or 1" which are disposed in overlapping spaced relation and connected in series circuit relation by the connecting piece a which is of c0nducting material and hence traversed. by current. The strip Z to the lower end of which is fastened'the' current connecting terminal a may, for example, bend to the left, that is tosay, on becoming heated its upper end f flexes to the left; on the other hand the strip 7' which carries its connecting terminal I; at the upper end may bend to the right. that is, itslower end you becoming heated flexes to the right. With the two ends 7 and g electrically connected with one another by the strip 0, the whole bimetallic formation may be traversed by current, for example, in the direction of the arrow. The conditions as regards length and position of the bimetallic strips Z and r and of the connecting piece a are so chosen that on the bending of the ends {1 and f whichat least in the range of temperatures coming into practical considerationdescribe approximately an arc, the distance apart of f, g is practically always the same so that no tensile or compressive stresses worth mentioning occur in the parts l, 1 or 'c. Fig. 1 shows the strips in the bent position whilst in the case of normal temperature they lie approximately in the direction of the main axis shown in dotted lines. The bisecting axis h of the connecting piece 0 is then the centre of a circular movement and can transmit the latter without any further auxiliary means on to a pointer, contact arm, or releasing lever. v

Fig. 2 shows more in detail the practical form of construction of this combination, the letters having the same signification as inFig. 1. The connection between the strips land 1' on the one hand and the connecting piece a on the other can be effected by the rivet connections and k as indicated in the drawing; I

Another advantageous effect is obtained if, corresponding to Figs. 3 and 4, in place of the plain conducting connecting piece a a bimetallic strip 0 is inserted. In the figures there is represented a bimetallic strip 0 bending to the left and serving as a connect- I ing piece between the strips Z1 and 1". With this arrangement the bending of the bimetallic end f is considerably greater than in the arrangement previously described because the end f is also pressed towards the left by the connectingjstrip 0.

In place of individual bimetallic strips several placed beside each other can be used so that a bundle formation is obtained as shown in Fig. 5. Preferably the corresponding bimetallic strips Z' and 1", in this case are butt connected with their connecting pieces m and n.

'W hat we claim s new and desire to secure by Letters Patent of the United States, is:-

1. In a thermal responsive device, the combination comprising a pair of oppositely flexing bimetallic strips, each having one end fixed, and a member rotatably supported by the other ends of said strips.

2. In a thermal responsive device, the

combination comprising a pair of opposite-' ly flexing bimetallic strips disposed in overlapping spaced relation and a member extending between the overlapping ends of said strips and secured thereto to be rotated about an axis intermediate its ends upon simultaneous flexure of the strips.

3. In a thermal responsive device, the

combination comprising a pair of oppositely flexing bimetallic strips disposed in overlapping spaced relation, and a bimetallic member mechanically interconnecting the overlapping ends of said strips 4. A thermal current responsive device comprising a pair of oppositely flexing bimetallic strips, each having a circuit connecting terminal at one end thereof, and

a rotatable current conducting member elec' trically and mechanically interconnecting the other ends of said strips.

5. A thermal current responsive device V comprising a pair of oppositely flexing bi- KURT MULLER. 

